The American military and unnamed allies have conducted what the Pentagon called “an extraordinary flight” over undisclosed Russian-controlled territory to send a message to Moscow, the U.S. disclosed Thursday.

A Pentagon statement revealed few details about what kind of aircraft, how many were were involved, or exactly where they flew. “The timing of this flight is intended to reaffirm U.S. commitment to Ukraine and other partner nations,” the statement said.

The 2002 Treaty on Open Skies establishes a regime of unarmed aerial observation flights over the territories of its signatories, according to the State Department.

The Pentagon said the unarmed flights were a show of resolute support for the security of European nations.

“Russia’s unprovoked attack on Ukrainian naval vessels in the Black Sea near the Kerch Strait is a dangerous escalation in a pattern of increasingly provocative and threatening activity,” the statement said.

“The United States seeks a better relationship with Russia, but this cannot happen while its unlawful and destabilizing actions continue in Ukraine and elsewhere.”